ET25SWE0022 - Laboratory Testing of Variable Capacity Heat Pumps to Develop Building Energy Modelling Performance Maps

This project aims to collect performance data of Residential Variable Capacity Heat Pumps (VCHPs, <5.4 tons) through Laboratory testing to generate a full operating envelope performance map of the equipment, accurately replicating unit performance in the field.  Currently, there are no publicly available performance data on VCHPs with this level of detail. The data collected as part of this effort will be used to generate regressions for use in building energy modeling software such as EnergyPlus. This information will be then used to generate more accurate ex-ante savings estimates for VCHPs in the California Electronic Technical Reference Manual (eTRM), which will improve the accuracy of program offerings that promote VCHPs. 

Accurate modeling of VCHPs is critical in the ongoing effort to appropriately incentivize the technology in California. VCHP is a heat pump equipment capable of achieving three or more steps of space conditioning capacity. VCHPs are significantly superior relative to two-stage HPs due to the fact that peak cooling and heating loads are rarely aligned for a given building in California

Since a single piece of equipment will serve both cooling and heating loads, significant amounts of cycling will result unless the equipment can modulate its capacity delivery rate. Manufacturers have responded to this opportunity with product offerings, with most manufacturers offering unitary and split VCHPs less than 5.4 tons and multi-split VCHPs greater than 5.4 tons (otherwise known a variable refrigerant flow systems).

Despite the prevalence of residential VCHPs (<5.4 tons) on the market, California's deemed modeling tools largely treat the equipment as equivalent to two-speed heat pumps, likely underestimating potential savings and leaving significant opportunities unaccounted for. 

This project would focus specifically on the building energy modeling data gap for residential VCHPs <5.4 tons in DEER by undertaking a laboratory testing effort to generate a full operating envelope performance map for the equipment at the full range of indoor and outdoor ambient dry- and wet-bulb temperatures.  This testing will replicate unit’s behavior in the field as much as possible, particularly, the unit’s full range of capacity levels across ambient temperature envelope under both cooling and heating modes. The research team will test up to three systems to ensure that test results reflect a representative level of equipment diversity. The project team will develop and execute a methodology for distilling down the test data into a singular representative performance map and then will seek input from other stakeholders to help inform product selection.  Coordination with product manufacturers will be pursued to ensure that testing is conducted with their buy-in and collaboration.

The test results will be converted into performance curves that are optimized for use in EnergyPlus. The team will coordinate with the CPUC ex-ante team for this data to ideally include these results in DEER2028.